My husband and I file Federal tax jointly. He's a part time resident in Michigan and when he filled out the MI 1040 form, it asks for the date of living in the state (from... to... ) for him and me. If he left my date out, the software will think it is an error. How can I get around that? Can I just put down one hypothetical date?

Put the same date as your husband. As long as the tax calculations are accurate, the Michigan tax authorities will not care.

Just to follow up - you said he "is a part time resident" of MI, not "was a part-year resident." Which makes me wonder whether he has permanently moved out of MI, or was he out of state only temporarily? It makes a difference - if he moved away intending to make his new state his principal abode then he shouldn't owe taxes to MI on his income during that period. But if he moved only temporarily - less than 6 months - and then moved back then MI could consider him a MI resident throughout the entire year. Also, I wonder whether your husband is filing a part-year resident tax return in the state that he moved to?

Good catch, ebaines. The devil is in the details!